"The Army and navy have been instructed to tighten security," President Felipe Calderon said after an overflight of the worst-hit areas of Veracruz.

The storm roared ashore on Friday, pummelling a country already reeling from one of its wettest seasons on record and leaving communities flooded from the border with the US state of Texas clear down to Mexico's Pacific coast states.

"In total we have the death certificates of 12 people," Civil Defence force director Laura Gurza told a meeting assessing the damage caused by hurricane, the first of the 2010 Atlantic season to make landfall.

Calderon toured damaged areas in Veracruz on the Gulf coast, where at least seven people were killed and about 10 more remained missing, according to authorities.

Karl forced the evacuation of oil rigs in the Gulf of Mexico and the shutdown of the country's nuclear power plant, located just four kilometres from where the hurricane roared ashore.

Among the dead were two men whose car was swept away by a flash flood in a river, a woman and her two children who drowned in their own home, and two people whose bodies were found washed up on a beach in the port of Veracruz.

Landslides also killed two women in central Puebla state, while one woman died and eight people were injured when a mudslide swept away a house in the southern state of Oaxaca.

Authorities did not immediately say where the two other deaths occurred.

Calderon inspected the flooding in several villages in Veracruz, whose governor Fidel Herrera said 112 of the 274 municipalities in the state remained under water.

Herrera said at least half a million people in Veracruz were affected in varying degrees by the hurricane. Some 40,000 people were evacuated to shelters.

Looting of small businesses was reported in communities near Veracruz, with authorities detaining 11 people and ordering in extra security personnel to try to maintain order.

Local media showed residents of many small towns making off with cases of beer, food and other goods apparently after snatching them from damaged stores.

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